The present disclosure relates to image reading devices and image forming apparatuses and particularly relates to a technique for controlling the intensity of light applied to an image reading section in detecting the size of an original document to be read.
Image forming apparatuses, such as multifunction peripherals, are equipped with an image reading device operable to optically read an original document placed on an original glass plate to generate image data. Among such image reading devices are those configured to detect the size of an original document on the original glass plate immediately before an original cover is closed.
The detection of the size of an original document is performed by irradiating the original document with light from under the original glass plate with the original cover open and reading the reflected light. Since during the detection of the size of the original document light is applied to the original document from under the original glass plate with the original cover open, intensive light through the original glass plate is directed to the operator. To cope with this, a technique is proposed of making the light intensity during the detection of the size of an original document with the original cover open smaller than the light intensity during image reading to keep intensive light from entering the operator's eyes during the detection of the size of the original document.